Colons often get confused with semi-colons, but they have different effects. The colon makes the first part of the sentence unimportant. It’s always the second part of the sentence that will give you the relevant information, although you need the first part of the sentence to tell you that.
Colons are used to make lists,
Don’t forget: clean the kitchen, do the shopping, and bathe the dog.
Here’s the grocery list: eggs, milk, juice, bread, and fruit.
To do: English essay, math homework, and write that thank-you note to Grandma.
People often abuse punctuation; for examples: commas, apostrophes and hyphens.
or to separate one idea from the one which follows.
I know what to do with that cake: eat it.